In May, 2017, a twenty-two-year-old Dutch entrepreneur named Boyan Slat unveiled a contraption that he believed would rid the oceans of plastic. In a former factory in Utrecht, a crowd of twelve hundred people stood before a raised stage. The setting was futuristic and hip. A round screen set in the stage floor displayed 3-D images of Earth; behind Slat, another screen charted the rapid accumulation of plastic in the Pacific Ocean since the nineteen-fifties. Slat is pale and slight, and has long brown hair that resembles Patti Smith’s in the “Horses” era. He was dressed in a gray blazer, a black button-down, black slacks, and skateboarding sneakers, which he wears every day, although he doesn’t skateboard. Onstage, he presented plastic artifacts that he had collected from the Pacific during a research expedition: the back panel of a Gameboy from 1995, a hard hat from 1989, a bottle crate from 1977. “This thing is forty years old,” he said in Dutch-inflected English. “1977 was the year that Elvis Presley left the building for good, presumably.” The audience laughed. Slat then held up a clear plastic dish, filled with shards of plastic. “The contents of this dish are the actual stomach contents of a single sea turtle that was found dead in Uruguay last year,” he said. A picture of the dead turtle flashed on a screen behind him.

Then Slat made his pitch. In the next twelve months, he and a staff of engineers at the Ocean Cleanup, an organization he founded in 2013, would build the system they had designed, assemble it in a yard on San Francisco Bay, then set sail with it, travelling under the Golden Gate Bridge and out into the Pacific. Slat’s destination was the Great Pacific Garbage Patch, midway between California and Hawaii, an area within what is known as the North Pacific Subtropical Convergence Zone. The patch is not, as is often believed, a solid island of trash but a gyre, twice the size of Texas, where winds and currents draw diffuse floating debris onto a vast carrousel that never stops.

There are four other ocean gyres in the world, but scientists believe that the one in the North Pacific contains the most trash—nearly two trillion pieces of plastic, weighing nearly eighty thousand metric tons, according to a study that scientists working with the Ocean Cleanup published in the online journal Scientific Reports last March. The study found that ninety-two per cent of the pieces are large fragments and objects: toothbrushes, bottles, umbrella handles, toy guns, jerricans, laundry baskets. Most problematic, and accounting for half of the plastic mass in the gyre, are what sailors call ghost nets: great tangles of mile-long discarded fishing nets weighing as much as two tons, which can ensnare animals such as seals and sea turtles. Attempting to fish out this drifting morass of trash using conventional methods—vessels, more nets—would be a Sisyphean task.

Slat became famous for a TEDx talk that he gave in 2012, in which he expounded on an idea that he had after a scuba-diving trip in Greece during high school. Instead of trying to catch ocean plastic, he thought, perhaps we could let the plastic come to us. “The oceanic currents moving around is not an obstacle—it’s a solution,” he told the audience. Slat, eighteen years old at the time, had entered an aerospace-engineering program at the Delft University of Technology and then, in keeping with the Silicon Valley archetype, dropped out before his second semester. But he had a big, vivid idea, a sweetly tremulous voice, and a goofy sense of humor. (His Twitter bio reads, “Studied aerospace engineering, becomes a cleaner.”) The video went viral, and Slat soon crowdfunded two million dollars from donors in a hundred and sixty countries. The United Nations Environment Programme named him a 2014 Champion of the Earth, noting his “keen mind” and “the lack of fear that marks out visionaries.” The jury for the world’s largest prize for design, the Danish INDEX: Award, granted him a hundred thousand euros, stating that his “incredibly ingenious idea will greatly improve the condition of the Earth’s greatest natural resource, as well as the lives of millions.” To date, Slat has hired eighty employees and raised some forty million dollars from donors online, charitable foundations, the Dutch government, a few anonymous Europeans, and Silicon Valley billionaires like Peter Thiel and Marc Benioff. After many iterations and scale-model tests of his invention, he and his team settled on a design.

The mechanism that Slat revealed in Utrecht was surprisingly simple: a two-thousand-foot floating plastic boom, attached to a geotextile skirt that would extend about ten feet beneath the ocean’s surface. The boom and the skirt would together create an artificial coastline that would accumulate flotsam riding the gyre’s currents, eventually forming a sort of shoreline of concentrated trash. Onstage, Slat gave a signal, and a black curtain behind him fell from the ceiling to reveal four monumental anchors. These were, Slat said, key to the concept. They would hang hundreds of metres deep, where the currents are much slower than at the top, insuring that the system moved more slowly than the trash, rather than just drifting around with it.

At regular intervals, Slat explained, a ship would transport the trash back to land, where it would be recycled. Some of it would be turned into plastic products (sunglasses, phone cases, chairs), which the Ocean Cleanup could sell to generate revenue for more systems. He expressed the hope that, by 2020, there would be sixty devices in the gyre; in five years, he said, they would have removed half of its trash. By 2040, Slat promised, he could clear ninety per cent of the trash from the North Pacific gyre.

The Monday after the announcement, Slat arrived at the Ocean Cleanup’s headquarters, an airy, modernist office in Delft. He was in high spirits. “We were at peak enthusiasm,” he told me later. Online donations were rising, and his in-box was full of congratulatory notes. His first meeting of the day was with his top engineers. They did not look cheerful. The lead engineer said that they had been running some new tests. They had not properly accounted for the power of “wave drift force”—the accelerating energy of the surface waves absorbed by the device—which would cancel out the drag of the anchors. The design would not work. Slat recalls the engineer saying, “We’re going to have to do it slightly differently.” There were some possible solutions, the engineer said. How about losing the anchors, allowing the device to race after the trash? Slat grew very quiet. “It was a bit stressful,” he said. “Like, whoops.”

In 1941, two British chemists, V. E. Yarsley and E. G. Couzens, published an article in Science Digest that imagined “a dweller in the ‘Plastic Age.’ ” This Plastic Man, they wrote, “will come into a world of color and bright shining surfaces, where childish hands find nothing to break, no sharp edges or corners to cut or graze, no crevices to harbor dirt or germs.” As the chemists had predicted with surprising accuracy, “tough, safe, clean” plastic was soon everywhere. By the mid-nineteen-sixties, fifteen million tons of plastic were being produced every year. By 2015, the annual total was nearly thirty times greater.

Of all the plastic waste ever created, only about nine per cent has been recycled. Seventy-nine per cent rests, forgotten, in landfills, dumps, forests, rivers, and the ocean. In recent years, less than fifteen per cent of the plastic packaging produced annually has been recycled—the sort of figure that has led Jane Muncke, the director of Zurich’s Food Packaging Forum, to describe recycling as “the fig leaf of consumerism.” The scale of the problem has been difficult to communicate to the public. In the past, images of animals, like the one that Slat showed in Utrecht, have mostly made the biggest impact. In the eighties, photographs of birds and turtles stuck inside six-pack rings caused a public outcry, and eventually the Environmental Protection Agency mandated that ring carriers be biodegradable. In 2005, a picture of Shed Bird, a six-month-old Laysan albatross, whose sliced-open belly revealed a collection of lighters, bottle caps, and other plastic scraps, became an environmental icon, a symbol of our careless throwaway lives. More recently, viral photos and videos have elevated the cause: a dead sperm whale that washed ashore in Indonesia with thirteen pounds of plastic in its stomach, a sea turtle with a drinking straw wedged up its nostril.

In 2015, the environmental engineer Jenna Jambeck co-authored a study, published in Science, in which she calculated that an average of eight million metric tons of land-based plastic entered the oceans each year: the equivalent, she wrote, when she testified about the problem before Congress, in 2016, of “five grocery-size bags filled with plastic going into the ocean along every foot of coastline in the world.” By 2025, she has said, those five bags will be ten. “That got a tremendous amount of pickup and really helped people understand the vastness of scale,” Janis Jones, the C.E.O. of the Ocean Conservancy, a D.C.-based environmental-advocacy group, told me. Sometimes the simplest comparisons have been the most effective. Another report, published by the Ellen MacArthur Foundation, predicted that by 2050 there could be more plastic than fish, by weight, in the oceans.

One of the pioneers of plastic-pollution research, and of conveying the findings in tangible images, was Charles Moore, a horticulturist and oceanographer who, in the nineteen-nineties, observed an alarming amount of garbage in the sea while sailing between California and Hawaii. Moore began taking researchers to the gyre, dragging nets alongside his catamaran and cataloguing the contents. In 2001, Moore published the results of his studies: there was six times more plastic in the gyre, by mass, than there was zooplankton, the base of the food chain. Moore—charmingly grumpy, often with a map of the gyre and a dish of plastic shards in hand—went on to discuss the Great Pacific Garbage Patch on the “Late Show with David Letterman,” “The Colbert Report,” and “Good Morning America.” The image of the patch proved resonant, if misleading. Soon people were saying that you could walk on it and even spot it from outer space.

In fact, most of what Charles Moore found was not large pieces of debris but microplastic—the tiny fragments that remain when the sun breaks down the larger hunks, and which the scientist and former U.S. marine Marcus Eriksen has called “the smog of the sea.” In 2008, Moore hosted Eriksen and an ocean-policy analyst named Anna Cummins on one of his expeditions; the two got married and later co-founded a nonprofit called the 5 Gyres Institute, which made research expeditions all over the world. In 2014, Eriksen, Moore, and seven other co-authors published their findings in the online journal PLOS One: more than 5.2 trillion particles of plastic were swirling in the planet’s oceans, and, in time, much of it would be ingested by ocean dwellers and by creatures that eat fish, including people.

Since then, numerous studies have shown that microplastic is everywhere—in the melting ice of the Arctic, in table salt, in beer, in shrimp scampi. A study last year found traces of it in eighty-three per cent of tap-water samples around the world. (The incidence was highest in the United States, at ninety-four per cent.) A major concern of scientists is that chemical toxins in the microplastics may leach off during digestion, gradually building up in animal and human tissues. Judith Enck, a senior official at the Environmental Protection Agency under President Obama, told me, “Where we are on plastics is where we were fifteen years ago on climate change. We’re just beginning to get the picture.”

The looming public-health crisis has bolstered environmentalists’ arguments that the priority of governments, N.G.O.s, and the public ought to be preventing plastic from entering the ocean in the first place. According to some analyses, a forty-five-per-cent reduction in the leakage of plastic from land to sea is possible by improving waste management in China, Indonesia, the Philippines, Thailand, and Vietnam. In the Philippines, Froilan Grate, an anti-plastic activist and organizer who has worked with Eriksen and Cummins, has helped establish zero-waste management systems in cities including San Fernando, which has set up citywide composting and recycling, created wage-paying jobs for garbage collectors, and banned plastic bags. Grate, who is working with sixteen cities across Indonesia, Malaysia, and India, estimates that San Fernando’s new system has prevented fifty-one thousand tons of plastic from entering the environment. But funding for such projects is scarce. When I asked Grate about Slat’s plan to remove the plastic from the ocean, he said, referring to the money that Slat had raised, “If I had forty million dollars, I could set up zero-waste programs all over Asia.”

In 2017, the Ocean Conservancy joined with industry heavyweights to announce that they were fund-raising for investments in recycling companies in Southeast Asia. The initiative grew into an investment-management firm, Circulate Capital, to which companies such as PepsiCo, Dow, Unilever, and Coca-Cola have pledged more than a hundred million dollars. Some efforts to ban the production of single-use plastics are succeeding—and not just in countries like Kenya, which addressed its litter crisis in 2017 by decreeing that anyone caught producing, selling, or even carrying a plastic bag could go to prison for four years or face a fine of up to forty thousand dollars. In October, the European Union advanced a directive to roll out bans on single-use plastics like plates and cutlery. In the United States, thanks to a campaign led by Eriksen and Cummins, microbeads—the exfoliating plastic sprinkles common in toiletries—became illegal in 2018. New York City has banned most polystyrene food containers. Straws, thanks in part to the turtle video, have become a favored cause: California has restricted their use, and Starbucks plans to phase them out altogether by 2020. Lego is introducing a new plant-based form of plastic.

According to Eriksen and other environmentalists, the Ocean Cleanup is a “distraction from the real solutions that the entire global movement is now working on.” And yet it is undeniable that the plastic already in the ocean will not simply disappear without a trace. In this dire moment, people are desperate for heroes. Slat agrees that prevention efforts are urgently necessary. “For us to be successful, that part needs to be taken care of as well,” he told me. But, he added, “all that large stuff will become the small, dangerous microplastic, and then we’ll be in a much worse position.” Given what Slat sees as the inevitable torpor of political change, he believes it is his job to remove plastic from the gyres before it degrades into tiny particles, making the smog worse. “The sooner we get it out, the better,” he said.

Unlike Moore and Eriksen, Slat has never sailed from California to Hawaii. “I do enjoy being at the ocean, like most people, but not so much being on the ocean,” he told me on a visit to New York after the Utrecht event. In 2015, he spent eight days surveying plastic in the Bermuda Triangle, during which he was violently seasick. Slat cares deeply about the environment, but, for him, the appeal of cleaning the oceans is also about puzzle solving. “There’s no better feeling than having an idea and seeing it become reality, emerging in the physical world,” he said.

Still, he knows that people need a story if they’re to get behind his idea. “Don’t get me wrong,” he told me, over tea in a downtown café with Joost Dubois, the fifty-seven-year-old head of communications for the Ocean Cleanup. “The trigger, the passion that made me want to do it, was its bigger significance, which you get from things like the experience I had scuba diving.” On Slat’s scuba-diving trip to Greece, when he was sixteen—as he has said in countless talks and presentations—he saw more plastic bags than fish. At the mention of the well-worn anecdote, he shot Dubois a conspiratorial glance, and they laughed.

Slat had with him a black backpack decorated with sew-on patches from the Ocean Cleanup’s plastic-counting research expeditions, and he was wearing his usual skateboarding sneakers. If I didn’t know him, I might have mistaken him for a high-school student. Many of his supporters recall his youthful demeanor, as well as his ageless poise, as having won them over. Laurent Lebreton, the lead oceanographer for the Ocean Cleanup, described him to me as “a very smart boy.”

Slat was born in Delft, a marine-engineering hub, and grew up in the historic city center, a few blocks from where Johannes Vermeer once lived. Slat’s mother, Manissa Ruffles, who worked as a city tour guide, brought him up alone. Slat’s father, a painter, lives in Croatia. Ruffles told me that, from a young age, Slat acted like a grownup and preferred D.I.Y. fairs to amusement parks. When he was two, he built a small but functional chair out of wood and nails.

In primary school, Slat lost a front tooth after some classmates shoved him into a wall; he now has a chipped crown. The bullying was relentless, he recalled. “Whenever I used to do sports at school, there were those children who were picked last,” he said. “I just wasn’t picked at all.” After switching schools when he was twelve, he made friends with other tinkerers. He started building rockets, then attempted to build a bottle-rocket-powered contraption that would launch a friend into the air. That idea had to be abandoned, but when he was fourteen he managed to get two hundred and thirteen people to stand in a field at Delft University and simultaneously hand-launch bottle rockets. The event established a Guinness World Record.

After the Tedx talk, and his subsequent decision to drop out of university, Slat taught himself more about ocean plastic, oceanography, and engineering. He is the only member of his research team who does not have an advanced degree. But, according to Arjen Tjallema, the technology manager, he keeps pace. Rick Spinrad, one of the members of the Ocean Cleanup scientific advisory board, and, until 2016, the chief scientist for the National Oceanic and Atmospheric Administration, recalled having been skeptical when he first met Slat, in 2016: “I started asking more technical questions, on windage and the relative velocity of plastic particles, on what physical oceanographic models he was considering using. His answers were sophisticated, savvy, and quite candid. When he did not have the tech answer, he certainly knew how to get that answer. It was obvious to me that he had been talking with the right folks.” The list included scientists at the Delft University of Technology and at the Royal Netherlands Institute for Sea Research.

Slat also had to learn how to build a startup. “There were mistakes,” he told me. He hired one man who he thought had an excellent résumé, with forty years of offshore engineering experience. After a few months, the man told Slat that what they were trying to do was impossible. He did not remain on the job. “We don’t have any glass-half-empty people,” Dubois said.

Slat was spending more time flying around the world in order to network. His mother, with whom he still lived, told me that she sometimes worried about him. “He was always among middle-aged people in gray suits,” she said. “I feel he skipped his adolescence.” Slat now receives fifty speaking requests every day. As the face of the organization, he knows that such appearances are obligatory. “It’s not something I can delegate,” he said. He learned early on, from his success on social media, that people wanted what he was proposing—in particular, he said, a solution that would not mandate that anyone make a huge sacrifice. Slat is an admirer of Elon Musk. “He understands how human psychology works, just like the Ocean Cleanup,” Slat said. “We don’t say, ‘Ban all the plastic’—we sort of provide an alternative that’s better, that’s exciting, that fits into a world view that you can be excited about.” Jennifer Jacquet, a professor of environmental studies at New York University and the author of the book “Is Shame Necessary?,” believes that Slat’s success goes beyond “technological solutionism,” or the “TED Talk obsession.” “We always love the idea of cleanups more than we love the idea of prevention, or mitigation,” she said. “We love treating illnesses more than we do preventing them. But our affinity for simplistic solutions isn’t innate; they’re narratives we’ve been sold.”

In the café, Slat’s phone started buzzing. A video of an interview he had done earlier in the day, with Luke Rudkowski, a right-wing activist and videographer, had just gone online. Slat seemed nervous about what he had said. The subject of the interview was the Bilderberg Meetings, an annual off-the-record forum of international leaders, which he had attended the previous weekend, in Chantilly, Virginia. “It’s very secretive,” Slat said. “It’s like Davos, but with just a hundred people. The King of the Netherlands was there, David Petraeus. A lot of people think it’s some sort of conspiracy thing.” Rudkowski, for instance, referring to the Bilderberg participants, had asked Slat how his mission to clean the oceans would “work with their world-domination plan.”

It was sunny and warm, and Slat suggested that we take a walk. “When you walk, your brain is working better,” he said. “More blood flow.” We headed west to the Hudson River. Passing a small marina, we stopped, leaning over the railing to look at the dark, oily water. Dubois pointed at a drifting cigarette butt—cigarette filters are made of cellulose acetate that leaches toxins into waterways. “Ocean plastic,” he said. “Not ocean plastic yet,” Slat noted. “Will be soon,” Dubois said.

Just that morning, Nature Communications had published a paper by Slat, the oceanographer Lebreton, and four other scientists which estimated that as much as 2.4 million metric tons of plastic could be entering the ocean from rivers each year. Slat is often asked whether he will develop a cleanup system for river mouths, catching the plastic at its source. A few river-mouth systems have already been successfully deployed, including three in Baltimore known as Mr. Trash Wheel, Professor Trash Wheel, and Captain Trash Wheel. Universally celebrated by scientists, and citizens, they are arguably the most beloved and sensible anti-plastic-pollution mechanisms in the country. Slat has a few ideas for river projects down the road, but, he said, “if you do everything at the same time, you’ll succeed at nothing.”

We walked around the southern tip of Manhattan, then cut back inland to a park in Chinatown, the spot Slat had chosen for his next meeting. A tall man wearing a tuxedo and a woman in an evening gown appeared from between two parked cars and crossed the street toward us. The man was Hugh Welsh, the head of DSM North America, an arm of a Dutch multinational company that manufactures products including resins and plastics for the building and automobile industries, electronics, medical equipment, and food packaging. Dubois greeted Welsh warmly; he used to work as a public-relations director for DSM, and Welsh has become a major donor to the Ocean Cleanup. Welsh and his colleague apologized for their attire; they were on their way to a black-tie event.

In recent years, environmental groups such as Upstream and the international movement #BreakFreeFromPlastic, which Froilan Grate helps lead, have argued for what’s become known as “extended producer responsibility”—the idea that the manufacturers of products that become waste must bear the burden of cleaning it up, especially when they send those products to developing countries that have little solid-waste disposal or recycling infrastructure. Slat’s model, which relies on voluntary donations, might seem a good place to start, or, conversely, a compromise that will make plastic producers feel better about doing little to address the problem at its source. An entire fleet of sixty of Slat’s systems could cost around three hundred and sixty million dollars, and Slat hopes that much of this will come from corporations that have a stake in the production of plastic.

Slat politely greeted Welsh, who seemed amused and intrigued by the young Dutchman, as if he were meeting a child celebrity. “Is this your first time to New York?” he asked. Slat, who had been to the city many times before, said, “No, but it’s even more interesting every time.” Dubois and Welsh walked ahead, and Slat bid me farewell. It would be a private meeting. Slat later told me that he hoped companies like DSM, “or anyone who wanted to help the ocean,” would start sponsoring systems. “They would have plenty of space for logos, if there is any company out there that wants to be smart,” he said.

I met Slat again ten months later, in April, at the bleak waterfront assembly yard in Alameda, across the bay from downtown San Francisco. A tower housing Marc Benioff’s company, Salesforce, stood high on the skyline. Across from a row of ancient school buses awaiting retrofits, a turquoise Ocean Cleanup sign announced the presence of the prototype: “Home of System 001.” Resting on head-high risers was an enormous black plastic pipe, the first segment of the two-thousand-foot device’s boom. Workers were about to start the next fusion weld.

Slat’s original idea—using the ocean’s currents to do the work of collecting trash—has remained the foundation of his design, but almost everything else has changed. His first blueprint, presented at the TEDx talk in 2012, owed more to science fiction than to reality: a chain of manta-ray-shaped stations that would passively funnel trash into their bellies. In this model, an underwater system of mooring lines would anchor the entire structure to the seabed, fifteen thousand feet below.

In the summer of 2016, Slat launched a prototype called Boomy McBoomface (a suggestion from social-media followers) into the North Sea. Within two months, the ocean had torn it apart. Although Slat’s engineers were increasingly convinced that mooring a structure to the seabed would not work, Slat was reluctant to let go of the idea. “As an inventor, your inventions are your babies,” he said. Besides, he added, “it can be very risky if you leave an old idea and switch to a new idea too soon. It’s like a new girlfriend. You don’t see the flaws.”

As a banner at the assembly yard showed, the final blueprint had no anchors. Instead, it consisted of a free-floating boom, bent into the shape of a horseshoe, with a skirt secured to its underside. The new idea was that the device, driven by the forces of the wind and waves from outside the horseshoe, would act like a sweeper, reorienting itself when the wind changed direction. Models and tests suggested that the sweeper would travel about fifteen centimetres per second faster than the plastic and collect 2.2 metric tons of trash a week. G.P.S. trackers, cameras, and sensors positioned every hundred metres along the length of the boom would communicate the system’s progress to the team onshore, as well as indicate its presence to passing marine vessels and monitor for wildlife.

Longtime critics of the Ocean Cleanup, such as Miriam Goldstein, the director of ocean policy at the liberal think tank the Center for American Progress, have repeatedly pointed to the potential of Slat’s system to hurt the “ecological community” on the ocean’s surface, including jellyfish, water striders, and tiny creatures known as blue sea dragons. In 2014, Goldstein and another oceanographer, Kim Martini, expressed this and other concerns—such as the boom’s ability to withstand harsh offshore conditions—in a critique online. In response, Slat countered by saying that they were not engineers. But, he told me, he did not want to dismiss critics, because their contributions had helped transform the design of the system from his original concept. “All the details are different now, and it’s in part thanks to unsolicited feedback,” he said.

Goldstein and Martini remained skeptical. Stefan Llewellyn Smith, who teaches fluid mechanics at the Scripps Institution of Oceanography, also warned that successes in testing pools and in computer models were no guarantee that the system would behave the same way once it was at full size, out at sea. “I’d class the difference in velocity between the plastic and the structure as the main issue,” he told me. Gradually, Slat seemed to be absorbing such concerns, and, at the assembly yard, was more cautious in his promises than he had been earlier. “It still is very much an experimental system,” he said. Research equipment and tools would be sent out to the gyre with the device, and these would, in any case, benefit the scientific community, he stressed: “Always good to better understand the problem.”

Early on the morning of September 8th, the day of the launch, Slat dreamed that the pipe had been sent out into the seawater and had begun to melt. He woke up and could not get back to sleep, so he started preparing for the dozens of interviews he would give that day. The sky was blue, with light winds and warm air. When he arrived at the pier in San Francisco Bay, the top deck of the media boat, a ferry, was already packed with cameramen and reporters. The Ocean Cleanup’s publicity crew, seven strong, wore turquoise “Ocean Cleanup” shirts, which matched the turquoise-painted Maersk tug ship that would tow the system out to the gyre. Maersk, the largest shipping line in the world, was providing the ship and its crew free of charge. A Maersk spokeswoman named Stephanie Gillespie was aboard, and she told me, “Our seafarers sail through this garbage patch and see this plastic everywhere. So it made sense for our company to invest in cleaning it up.”

The team had given Slat’s invention a name, Wilson, for the volleyball that Tom Hanks, lost at sea, befriends in “Cast Away.” Slat held a brief press conference, concluding, “For sixty years, mankind has been putting plastic into the oceans. From this day onward, we’re taking it back out again.” The ferry set off, and a few minutes later Wilson came into view, gliding behind the Maersk ship like a long black tail. It was already speckled with bird droppings.

At the moment when the media ferry was behind the ship, as it approached the Golden Gate Bridge, Slat jumped up to stand on some benches at the bow for pictures, his hair blowing in the wind. Then a deckhand emerged from the bridge and yelled, “Please get down!” Slat, looking embarrassed, stepped off the bench. The journey back was fast and, once ashore, Slat collapsed on a flower planter along the boardwalk. “I’m dead,” he said. Dubois and a few other Ocean Cleanup staff were staring at their phones. Dubois started cheering: “We just got to a hundred thousand Instagram followers!”

A few days later, Goldstein, who had seen news of the Ocean Cleanup’s big day online, ran into Slat at a party hosted by Benioff at the Salesforce tower, during San Francisco’s Global Climate Action Summit. “Congratulations on the launch,” she said. “I hope it succeeds.” “You do?” Slat replied. Martini tweeted about the launch, posing three “critical questions” about the structure’s strength, efficacy, and impact on marine ecology. She said of Slat and his team, “I think they have overexaggerated what they can do, and that sells.” But despite all her doubts, she said, “at this point I kind of hope it works. Maybe they are going to prove me wrong. That’s my secret hope.”

In mid-September, Eriksen sent an e-mail blast to a Listserv called Marine Debris, in which he called Slat’s mission “a misdirected activity” that “makes it harder for those working to focus the narrative to prevention.” Eriksen reminded me, by phone, that only one per cent of the plastic entering the ocean is on the surface of the North Pacific gyre. Scientists still don’t know where, exactly, the rest goes. Eriksen explained that it might be on the seafloor, or suspended as nanoplastic, or have washed back onto the shore. A recent study on debris from the 2011 tsunami in Japan found that, of a thousand boats that the wave carried out to sea, only a hundred were estimated still to be offshore, travelling along the currents. “There are natural mechanisms that eject trash rapidly,” he wrote to the Listserv.

Five weeks after the launch, on October 16th, Wilson, towed behind the Maersk tug, arrived at the North Pacific gyre, a few dozen degrees of longitude east of the International Date Line. An Ocean Cleanup engineer had given Wilson its own Twitter feed, and its coördinates and pictures of its surroundings were posted almost daily. Each picture showed a portion of the pipe, and, when the sun was shining, sparkling blue water. There was no plastic in sight. A week later, Slat tweeted a picture: “First plastic.” Two bobbing white baskets and a scattering of fragments were visible in the waves.

As the weeks passed, Wilson behaved as the engineers hoped it would—reorienting itself when the wind changed direction, catching and concentrating plastic in its arms. But then much of the plastic would float away, back out to the infinite, or drift around Wilson and collect along its back. Slat’s engineers developed twenty-seven hypotheses to explain why this happened. Wilson was moving too slowly, sometimes slower than the plastic. Perhaps the surface plastic was more affected by the wave drift force than they had calculated, or perhaps an inertial current—one much smaller and more localized than the main one they had accounted for—was slowing Wilson’s motion. “This is, of course, something we never saw in the computer models, which underlines why it’s so important that we’re out there,” Slat said, when I met him in New York again, just before Christmas. “Another fun one is the jellyfish hypothesis,” he said. Scientists noticed that Wilson’s arms were oscillating, creating a propulsion that resembles the way a jellyfish swims, and causing Wilson to “swim” away from the plastic.

Slat had a cold, and hadn’t slept much for several weeks. Headlines had blared the system’s failure, and critics on Twitter scoffed at Slat’s boondoggle. “What I would be afraid of is that, if it fails, we let down the world,” he said. “People will point at it and say, ‘Look, fancy gizmos, silver bullet, panacea—basically, that proves that that is not the way to solve a problem.’ ” But his team of engineers had helped him “come to peace,” he said, as they all returned to work. He was already considering new iterations, possibly incorporating sails or wave gliders that would make Wilson go faster.

When I described Wilson’s plight to Chris Garrett, a physical oceanographer and an emeritus professor at the University of Victoria, he told me that he found the entire premise of the device “rather strange and puzzling.” He and other scientists pointed to additional phenomena—Stokes drift, Langmuir circulation, Ekman spiral—that could cause the plastic to move faster than Wilson. Spinrad described the Ocean Cleanup system as “medium-level technology,” with a high risk, and a high payoff. “The sea is an unrelenting trial judge,” he said. “The probability of failure was at least as high as the probability of success.” He added, “I see nothing that cannot be remediated with good physics and engineering and money.” The team has since stated that Wilson collected two metric tons of plastic.

A week and a half after Slat and I met in New York, crew members stationed in the gyre were doing a maintenance check of Wilson when they noticed that one end of the boom, an eighteen-metre segment, had snapped off and floated away, owing, apparently, to “material fatigue” on a small section. Perversely, Wilson’s plastic wasn’t durable enough. The segment was retrieved, and the two parts were towed to Hawaii, arriving just off the coast on January 17th. Dubois had been in Honolulu, trying to negotiate a way to bring Wilson into the harbor and onto a loading dock, either to be repaired in Hawaii or, if necessary, shipped back to the assembly yard in Alameda. When we spoke, he sounded determined, if weary. “The I-told-you-so’s have been pretty abundant,” he said. “But we’re not just a bunch of cowboys going out there to play with a big tube thing out in the ocean, trying to prove that we’re right. We want to show that this is an important research platform.” One of Slat’s funders, the grant foundation of the Swiss bank Julius Baer, recently gave the Ocean Cleanup an additional six hundred thousand dollars for research into safely recycling ocean plastic, which is brittle and often toxic. None of Slat’s other donors had indicated that they would stop supporting the Ocean Cleanup. Hugh Welsh told me that, despite the “unwarranted criticism that the project has faced,” he and DSM “remain steadfast supporters.” (In spite of repeated requests for an interview, Marc Benioff, Slat’s top donor, said that he was unavailable for comment.)

The last time I spoke to Slat, on January 7th, he was undeterred. “This is just a first act,” he said. “It’s not a system failure. It’s a component failure.” His words reminded me of an episode soon after Wilson’s launch, in Pacifica, a beach town south of San Francisco. Slat had learned that I surfed, and, despite being a beginner, he suggested that we go together. On the beach, he told me about a small rip in Wilson’s skirt that had occurred during the trip to the gyre. The skirt was Wilson’s most expensive component; it needed to be made by hand, and had required forty-eight people, working for sixty days, in a warehouse in the United Arab Emirates, to assemble. “That material seemed impenetrable, so it was a little hard to believe,” Slat said.

The wind was blowing onshore, turning the waves into a mess of white foam, and it was a long, exhausting paddle beyond the impact zone to calm water. Once there, Slat and I watched other surfers for a while, then Slat spotted a small ridge. He turned, paddled away, and disappeared. His board bobbed up to the surface without him, then he got tossed far back toward shore by the waves that followed. Some twenty minutes later, after another fight through breaking waves, he reappeared beside me. “Now I know how Wilson feels,” he said, gasping. “I feel sorry for him. So much power under there.” He sat on his board. Striving to catch his breath, he returned to Wilson’s journey to the gyre. “The skirt weighs twenty-seven thousand kilograms,” he said. “But when the swells are big enough it can flip out of the water like a flag in a hurricane.” As the afternoon passed, Slat stayed in the water, growing bolder, trying and failing to get up on his feet and ride a wave, washing to shore instead, then fighting the endless white water to get back out. ♦

This article appears in the print edition of the February 4, 2019, issue, with the headline “The Widening Gyre.”